1. Field of the Invention
The present invention relates to an optical disc system, and more particularly, to an optical disc system and method for efficiently controlling a sled motor thereof.
2. Description of the Related Art
Early record players used for recording and reproducing audio signals such as human voice or songs were in the form of phonographs. Then, audio tapes were developed and used. In the early record players and audio tapes, the audio signals were recorded in the form of analog signals. Since the 1980s, optical disc players have superceded the record players. The optical disc players use an optical device such as a laser to reproduce information stored in an optical disc. In the optical disc, a voice signal is stored after converted into a digital signal. The optical disc can store a large amount of data representing voice signals and has a longer life span, which makes the optical disc more widely used than the record. The optical disc system includes a compact disc player (CDP), a compact disc ROM (CDROM), a digital versatile disc player (DVDP), etc.
In a conventional optical disc system, a digital servo for a sled jump uses a pulse width modulation (PWM) output unit for controlling a sled motor. The PWM output unit receives a tracking error signal from a high frequency amplifier. A digital servo core receives the tracking error signal, performs tracking loop filtering, sled loop filtering, and sled average filter processing, and then provides PWM output control signal and PWM output signals for controlling the sled motor. The PWM signals are input to an integrated circuit (IC) device for controlling and driving the sled motor.
The use of conventional PWM output signals for controlling the sled motor produce noises, primarily, due to the large signal swing of the PWM signals. Also, a heat problem can occur in the IC device for driving the sled motor.
Therefore, a need exists for an optical disc system which can control a sled motor by use of control signals with reduced noises and more efficiently operate the sled motor control. Further, it will be advantageous to provide an apparatus and method of controlling a sled motor in an optical disc system with reduced problems caused by the heat generated by the IC device for driving the sled motor.
To solve the above and other problems, it is an object of the present invention to provide an optical disc system for efficiently controlling a sled motor in a sled jump.
To accomplish the above and other objects of the present invention, there is provided an optical disc system for reproducing data stored in an optical disc, the optical disc system having a sled motor for moving an optical pick-up; a digital servo core for filtering a tracking error signal provided from the optical pick-up to generate a first sled control signal and a second sled control signal; a microcomputer for generating a selecting signal, a third sled control signal and a fourth sled control signal for controlling the sled motor; a first selecting unit for receiving the first and third sled control signals and for selectively outputting one of the first and third sled control signals in response to the selecting signal; a second selecting unit for receiving the second and fourth sled control signals and for selectively outputting one of the second and fourth sled control signals in response to the selecting signal; a third selecting unit for providing the sled motor with the one of the first and third sled control signals from the first selecting unit in response to the selecting signal; and a fourth selecting unit for providing the sled motor with the one of the second and fourth sled control signals from the second selecting unit in response to the selecting signal.
Preferably, the optical disc system further includes a first digital-to-analog converter for converting an output of the first selecting unit into an analog signal to provide the converted output of the first selecting unit to the third selecting unit, and a second digital-to-analog converter for converting an output of the second selecting unit into an analog signal to provide the converted output of the second selecting unit to the fourth selecting unit. It is preferable that in the optical disc system, each of the first through the fourth selecting units is a multiplexer. It is preferable that in the optical disc system, the third selecting unit receives a first reference signal and outputs either the one of the first and third sled control signals or the first reference signal in response to the selecting signal, and the fourth selecting unit receives a second reference signal and outputs either the one of the second and fourth sled control signals or the second reference signal in response to the selecting signal.
The present invention also provides a method for controlling a sled motor in an optical disc system, comprising the steps of detecting a tracking error from an optical disc to generate a tracking error signal; filtering the tracking error signal to generate a first set of sled control signals to control a sled motor; generating a second set of sled control signals to control the sled motor in response to a command from a microcomputer in the optical disc system; and selecting at least one sled control signal from either the first set of sled control signals or the second set of sled control signals under control of the microcomputer, wherein the at least one sled control signal is provided for controlling the sled motor.